Members of this
family can be recognised by having 1 or 2 spines on the caudal peduncle
that is used for defence or fighting and can cause painful wounds on other
fish (or humans!) if provoked. The spines may even be venomous in some
species. The acanthurid fishes usually have highly compressed bodies and
a small mouth adapted to grazing algae. Some species also feed on plankton
and detritus. The family is commonly recognised on coral reefs around
the world and includes, besides the species usually considered the true
surgeonfish, also the unicornfish and the sawtails.